[RFC 01/60] sched: Store task_group->se[] pointers as part of cfs_rq

From: Jan H. SchÃnherr
Date: Fri Sep 07 2018 - 17:53:33 EST

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In reply to: Jan H. SchÃnherr: "[RFC 06/60] sched: Add a lock-free variant of resched_cpu()"
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Move around the storage location of the scheduling entity references
of task groups. Instead of linking them from the task_group struct,
link each SE from the CFS runqueue itself with a new field "my_se".

This resembles the "my_q" field that is already available, just in
the other direction.

Adjust all users, simplifying many of them.

Signed-off-by: Jan H. SchÃnherr <jschoenh@xxxxxxxxx>
---
kernel/sched/core.c | 7 ++-----
kernel/sched/debug.c | 2 +-
kernel/sched/fair.c | 36 ++++++++++++++++--------------------
kernel/sched/sched.h | 5 ++---
4 files changed, 21 insertions(+), 29 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 625bc9897f62..fd1b0abd8474 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5915,7 +5915,7 @@ void __init sched_init(void)
wait_bit_init();

#ifdef CONFIG_FAIR_GROUP_SCHED
- alloc_size += 2 * nr_cpu_ids * sizeof(void **);
+ alloc_size += nr_cpu_ids * sizeof(void **);
#endif
#ifdef CONFIG_RT_GROUP_SCHED
alloc_size += 2 * nr_cpu_ids * sizeof(void **);
@@ -5924,9 +5924,6 @@ void __init sched_init(void)
ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);

#ifdef CONFIG_FAIR_GROUP_SCHED
- root_task_group.se = (struct sched_entity **)ptr;
- ptr += nr_cpu_ids * sizeof(void **);
-
root_task_group.cfs_rq = (struct cfs_rq **)ptr;
ptr += nr_cpu_ids * sizeof(void **);

@@ -6746,7 +6743,7 @@ static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
int i;

for_each_possible_cpu(i)
- ws += schedstat_val(tg->se[i]->statistics.wait_sum);
+ ws += schedstat_val(tg->cfs_rq[i]->my_se->statistics.wait_sum);

seq_printf(sf, "wait_sum %llu\n", ws);
}
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 60caf1fb94e0..4045bd8b2e5d 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -385,7 +385,7 @@ void unregister_sched_domain_sysctl(void)
#ifdef CONFIG_FAIR_GROUP_SCHED
static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group *tg)
{
- struct sched_entity *se = tg->se[cpu];
+ struct sched_entity *se = tg->cfs_rq[cpu]->my_se;

#define P(F) SEQ_printf(m, " .%-30s: %lld\n", #F, (long long)F)
#define P_SCHEDSTAT(F) SEQ_printf(m, " .%-30s: %lld\n", #F, (long long)schedstat_val(F))
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b39fb596f6c1..638fd14bb6c4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4367,7 +4367,7 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
long task_delta, dequeue = 1;
bool empty;

- se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))];
+ se = cfs_rq->my_se;

/* freeze hierarchy runnable averages while throttled */
rcu_read_lock();
@@ -4421,7 +4421,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
int enqueue = 1;
long task_delta;

- se = cfs_rq->tg->se[cpu_of(rq)];
+ se = cfs_rq->my_se;

cfs_rq->throttled = 0;

@@ -7284,7 +7284,7 @@ static void update_blocked_averages(int cpu)
update_tg_load_avg(cfs_rq, 0);

/* Propagate pending load changes to the parent, if any: */
- se = cfs_rq->tg->se[cpu];
+ se = cfs_rq->my_se;
if (se && !skip_blocked_update(se))
update_load_avg(cfs_rq_of(se), se, 0);

@@ -7321,8 +7321,7 @@ static void update_blocked_averages(int cpu)
*/
static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq)
{
- struct rq *rq = rq_of(cfs_rq);
- struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)];
+ struct sched_entity *se = cfs_rq->my_se;
unsigned long now = jiffies;
unsigned long load;

@@ -9819,15 +9818,15 @@ void free_fair_sched_group(struct task_group *tg)

destroy_cfs_bandwidth(tg_cfs_bandwidth(tg));

+ if (!tg->cfs_rq)
+ return;
+
for_each_possible_cpu(i) {
- if (tg->cfs_rq)
- kfree(tg->cfs_rq[i]);
- if (tg->se)
- kfree(tg->se[i]);
+ kfree(tg->cfs_rq[i]->my_se);
+ kfree(tg->cfs_rq[i]);
}

kfree(tg->cfs_rq);
- kfree(tg->se);
}

int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
@@ -9839,9 +9838,6 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
tg->cfs_rq = kcalloc(nr_cpu_ids, sizeof(cfs_rq), GFP_KERNEL);
if (!tg->cfs_rq)
goto err;
- tg->se = kcalloc(nr_cpu_ids, sizeof(se), GFP_KERNEL);
- if (!tg->se)
- goto err;

tg->shares = NICE_0_LOAD;

@@ -9859,7 +9855,7 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
goto err_free_rq;

init_cfs_rq(cfs_rq);
- init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
+ init_tg_cfs_entry(tg, cfs_rq, se, i, parent->cfs_rq[i]->my_se);
init_entity_runnable_average(se);
}

@@ -9879,7 +9875,7 @@ void online_fair_sched_group(struct task_group *tg)

for_each_possible_cpu(i) {
rq = cpu_rq(i);
- se = tg->se[i];
+ se = tg->cfs_rq[i]->my_se;

raw_spin_lock_irq(&rq->lock);
update_rq_clock(rq);
@@ -9896,8 +9892,8 @@ void unregister_fair_sched_group(struct task_group *tg)
int cpu;

for_each_possible_cpu(cpu) {
- if (tg->se[cpu])
- remove_entity_load_avg(tg->se[cpu]);
+ if (tg->cfs_rq[cpu]->my_se)
+ remove_entity_load_avg(tg->cfs_rq[cpu]->my_se);

/*
* Only empty task groups can be destroyed; so we can speculatively
@@ -9925,7 +9921,7 @@ void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq,
init_cfs_rq_runtime(cfs_rq);

tg->cfs_rq[cpu] = cfs_rq;
- tg->se[cpu] = se;
+ cfs_rq->my_se = se;

/* se could be NULL for root_task_group */
if (!se)
@@ -9954,7 +9950,7 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
/*
* We can't change the weight of the root cgroup.
*/
- if (!tg->se[0])
+ if (!tg->cfs_rq[0]->my_se)
return -EINVAL;

shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
@@ -9966,7 +9962,7 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
tg->shares = shares;
for_each_possible_cpu(i) {
struct rq *rq = cpu_rq(i);
- struct sched_entity *se = tg->se[i];
+ struct sched_entity *se = tg->cfs_rq[i]->my_se;
struct rq_flags rf;

/* Propagate contribution to hierarchy */
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 4a2e8cae63c4..8435bf70a701 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -354,8 +354,6 @@ struct task_group {
struct cgroup_subsys_state css;

#ifdef CONFIG_FAIR_GROUP_SCHED
- /* schedulable entities of this group on each CPU */
- struct sched_entity **se;
/* runqueue "owned" by this group on each CPU */
struct cfs_rq **cfs_rq;
unsigned long shares;
@@ -537,6 +535,7 @@ struct cfs_rq {

#ifdef CONFIG_FAIR_GROUP_SCHED
struct rq *rq; /* CPU runqueue to which this cfs_rq is attached */
+ struct sched_entity *my_se; /* entity representing this cfs_rq */

/*
* leaf cfs_rqs are those that hold tasks (lowest schedulable entity in
@@ -1301,7 +1300,7 @@ static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
#ifdef CONFIG_FAIR_GROUP_SCHED
set_task_rq_fair(&p->se, p->se.cfs_rq, tg->cfs_rq[cpu]);
p->se.cfs_rq = tg->cfs_rq[cpu];
- p->se.parent = tg->se[cpu];
+ p->se.parent = tg->cfs_rq[cpu]->my_se;
#endif

#ifdef CONFIG_RT_GROUP_SCHED
--
2.9.3.1.gcba166c.dirty

Next message: Greg Kroah-Hartman: "[PATCH 4.4 06/47] drm/i915/userptr: reject zero user_size"
Previous message: Cedric Roux: "[PATCH v3 2/2] ARM: s3c24xx: Correct SD card write protect detection on Mini2440"
In reply to: Jan H. SchÃnherr: "[RFC 06/60] sched: Add a lock-free variant of resched_cpu()"
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